content: /**
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  
  package io.reactivex.observable;
  
  import io.reactivex.common.Disposable;
  import io.reactivex.common.annotations.*;
  import io.reactivex.common.functions.Cancellable;
  
  /**
   * Abstraction over an RxJava {@link SingleObserver} that allows associating
   * a resource with it.
   * <p>
   * All methods are safe to call from multiple threads.
   * <p>
   * Calling onSuccess or onError multiple times has no effect.
   *
   * @param <T> the value type to emit
   */
  public interface SingleEmitter<T> {
  
      /**
       * Signal a success value.
       * @param t the value, not null
       */
      void onSuccess(@NonNull T t);
  
      /**
       * Signal an exception.
       * @param t the exception, not null
       */
      void onError(@NonNull Throwable t);
  
      /**
       * Sets a Disposable on this emitter; any previous Disposable
       * or Cancellation will be unsubscribed/cancelled.
       * @param s the disposable, null is allowed
       */
      void setDisposable(@Nullable Disposable s);
  
      /**
       * Sets a Cancellable on this emitter; any previous Disposable
       * or Cancellation will be unsubscribed/cancelled.
       * @param c the cancellable resource, null is allowed
       */
      void setCancellable(@Nullable Cancellable c);
  
      /**
       * Returns true if the downstream cancelled the sequence.
       * @return true if the downstream cancelled the sequence
       */
      boolean isDisposed();
  
      /**
       * Attempts to emit the specified {@code Throwable} error if the downstream
       * hasn't cancelled the sequence or is otherwise terminated, returning false
       * if the emission is not allowed to happen due to lifecycle restrictions.
       * <p>
       * Unlike {@link #onError(Throwable)}, the {@code RxJavaPlugins.onError} is not called
       * if the error could not be delivered.
       * <p>History: 2.1.1 - experimental
       * @param t the throwable error to signal if possible
       * @return true if successful, false if the downstream is not able to accept further
       * events
       * @since 2.2
       */
      boolean tryOnError(@NonNull Throwable t);
  }
  